Formulation of standards and specifications for instruments and materials in dentistry requires development and evaluation of standard test methods that can be used in different laboratories with reliability. Standard test methods and test equipment ultimately lead to improvements in characteristics of dental materials and instrumentation usually through modification of existing products or development of new products in attempts to meet the minimum acceptance criteria of various specifications. The objectives of this proposal are: 1) to improve dental materials and instruments by development and evaluation of test methods, 2) to design or modify test dies, fixtures and instrumentation suitable for use in evaluation of dental instruments and materials, and 3) to evaluate physical, mechanical and chemical properties of dental instruments, equipment and materials which can be used in setting minimum quality limits in national and international specifications. This renewal request covers the following major areas: Endodontic instruments, pulp testers, composite resins, visible light curing devices, dentin bonding agents, silicate bonded investments, screen-film combinations, denture base resins and corrosion of crown and bridge alloys.